The present invention relates to a process for the preparation of polypyrrolidone by the polymerization of 2-pyrrolidone with one or more anionic catalysts and one or more polymerization accelerators.
As is already known, 2-pyrrolidone can be polymerized in the mass or in suspension in an inert liquid dispersion agent in which the polymer to be formed is totally insoluble or only slightly soluble. In the first case a lump of solid polymer is obtained or, if polymerization is carried out with stirring and monomer conversion is restricted, a crumbly polymer is produced. In the second case a granular or pulverulent polymer is produced. In all cases the polymer thus formed must be washed so as to remove unconverted monomer and catalyst residues. As a result of the required washing the polymerization is preferably carried out in suspension, because the product thus formed is more easily washed out.
From our own investigations the fact has emerged that on the one hand for the same polymerization period, in most cases polymerization in the mass gives higher conversions, while on the other hand polymerization in suspension gives a polymer with a higher molecular weight. The object of the present invention is a process for the polymerization of pyrrolidone, whereby--in as short a time as possible--a granular or pulverulent polymer is obtained having a molecular weight which is at least as great as that achieved using conventional procedures.